Expandable, sealed containers or bags are employed for collecting and temporarily storing gas emissions from motor vehicles before the collected emissions are analyzed by suitable test equipment. Such containers are expandable to a predetermined volume to collect a known quantity of gaseous emissions.
Typically, a plurality of such containers, such as six containers, are connected through suitable conduits, valves, etc., to a test apparatus to collect separate quantities of gas emissions from a vehicle and from ambient atmosphere. Samples of emissions from a motor vehicle under test are collected in the sealed containers as the motor vehicle is operated according to a prescribed test schedule corresponding to various engine operating conditions.
The expandable containers include a fitting sealingly mounted in each container which is connected to the test apparatus to receive gas emissions from the vehicle under test. The fitting directs the gas emissions into the container for storage, as well as enabling the stored gas contents to be evacuated from the container for subsequent analysis. The fitting and the sealed container are made of a chemically inert material, such as a fluorinated carbon plastic, i.e., plastics sold under the registered trademarks TEFLON, KYNAR, and/or TEDLAR.
In order to prevent wrinkling of the container when it is evacuated of gas and to insure complete inflation of the container to a constant volume without internal dead spots, small diameter, hollow conduits or tubes are disposed within the sealed container and connected in fluid flow communication with the fitting. The conduits have apertures formed along their lengths to draw gas from different parts of the container to prevent stratification of the gas within the container and to insure thorough mixing of the gas. Such conduits have been provided in a variety of shapes, such as a plurality of circumferentially spaced, straight segments, curved segments, etc.
An example of a fitting and gas conduit arrangement suitable for use in a gas emission sample apparatus is disclosed in U.S. Pat. No. 5,074,155. The fitting disclosed in this application has a small, smoothly tapered shape which minimizes dead spots in the container in the area of the fitting. Further, gas flow ports are formed in the fitting and receive gas conduits such that the gas conduits are arranged in a predetermined shape within the container to insure complete filling of the container to a constant volume and the complete evacuation of the stored gas from the container.
However, small gas emission containers for small sample volumes do not have sufficient interior space to enable the use of a gas flow conduit or conduits therein. Further, the economics of such small sample containers dictate away from the use of gas flow conduits and the associated, more complex fittings. However, such small gas emission containers must still be filled to a constant volume and, also, be completely evacuated of the gas contents for accurate test results. During storage and, particularly, during evacuation of the gas from the container, it is also important that the gas be distributed equally to all parts of the container and withdrawn from all parts of the container to overcome any stratification of the gaseous components that may occur.
It has also been found that while various fluoropolymeric sheet materials are inert, non-reactive and theoretically impervious to gas transmission. Gas permeability in sample bags composed of fluoropolymeric material such as TEFLON (polytetrafluorethylene), TEDLAR (polyvinyl fluoride), KYNAR (polyvinylidine fluoride) or HALON (polychlorotrifluoroethylene) has been greater than desired. In certain instances, it is believed that this is due to inadequate bonding characteristics between polymeric sheets composed of one or more of these polymeric materials. This has necessitated use of bonding agents, and multilayer materials in an attempt to achieve a robust flexible continuous seam between the respective fluoropolymeric sheets that are joined to produce an effective gas emission container. Heretofore such multilayer fluoropolymeric materials and bond regions did not provide the flexible, robust gas emission container in all situations.